Changing Tongue Depressor Position Between Rat Incisors of Both Jaws Varies Gastric Motility

The periodontal ligament between the wall of every tooth socket & the root of the tooth which it suspends allows slight tooth movement with each bite. This stimulates the ligaments' trigeminal mechanoreceptors (TMs) linked to the vagal motor n. stimulating motility of the antral region, demonstrating a periodontogastric motility reflex (Lorber, Can J Physiol Pharmacol 67:29‐35, 2000). To see whether maxillary or mandibular rat incisors might vary in performing this reflex, eight adult female rats were fasted 24‐48 h. During normal occlusion their molars occlude but not their incisors (Fig. 1A). Under pentobarbital, data were collected during three five minute periods. The first was the baseline(B) in which resting antral motility was observed. For the procedure period(P), a tongue depressor was placed vertically(V) (Fig. 1B) or horizontally(H) (Fig. 1C) between the incisors of each jaw. For (P) the mandible was closed every second for five minutes and antral motility observed. The last period was the postprocedural(PP) to note whether the antral effect extended beyond (P). Comparisons of the mean+1sd of (P) and (PP) with (B) revealed that in (V) the three values were 1.00+0.72, 1.39+0.94, 1.71+ 1.33, ANOVA P<0.04. In (H) the values were 1.00+1.45, 2.43+1.08, 3.98+1.17,ANOVA P<0.04. Comparing (H) and (V) by dependent t‐tests showed that (H) is greater in PP (P<0.05), presumably due to delayed greater stimulation of apically located TMs than those on the sides of the dental root, whereas the V position causes anterior stimulation of only the maxillary TMs and posterior stimulation of only the mandibular TMs. This may be because the primary location of the TMs is at the root apex from which they ramify, so fewer branches are stimulated at any location about the sides of the dental root than at its tip.